<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
		<script type="text/javascript">
			 var month = 30;
			 if (month < 1 || month > 12) {
			 	month = Number.NaN;
			 }
			 console.log(month);
		</script>
	</head>
	<body>
	</body>
</html>
